The present invention relates to an apparatus and a process for producing dentures having a synthetic resin base, and more particularly to an apparatus for producing such dentures which is adapted to execute all the steps of removing wax from a flask by heating a wax pattern therein, injecting and filling a synthetic resin into a pattern cavity formed by removing the wax and shaped in conformity with the denture, and polymerizing the filled resin, and to the process to be practiced by the apparatus.
In producing dentures having a synthetic resin base, it is common practice to use individual devices for performing the respective steps of removing wax from a flask by heating a wax pattern therein within a pot (see JP-B-4395/1995), injecting and filling a synthetic resin into the resulting pattern cavity (see Laid-Open Japanese Utility Model Application 21919/1993) and polymerizing the resin (see JP-B-4395/1995).
On the other hand, JP-B-9055/1986 discloses an apparatus for producing dentures having a synthetic resin base which comprises a set of devices for successively performing the three main steps, i.e., the steps of removing wax, injecting and filling synthetic resin, and polymerizing the resin. The production apparatus comprises in combination a portion for removing wax from a flask as placed in a flask tank using hot water, with a flask tank lid and a wax lid closed, a pressure device having a cylinder set in position with the tank lid closed and with the wax lid opened for injecting and filling a synthetic resin into the flask, and a portion for polymerizing the filled resin within the flask tank.
The flask for use in the production apparatus comprises two split segments which are prevented from separating from each other by being pressed against a side wall of the flask tank by a pressing device.
The conventional apparatus for producing dentures with a synthetic resin base has the following problems.
1. Since the flask is prevented from separating into the segments by being pressed against the flask tank wall by the pressing device, a strain is likely to occur in the resin if the flask is released from the pressing device before the resin is polymerized. Accordingly, when the flask filled with the resin is taken out from the tank and then heated for polymerization, impaired accuracy will result, so that the resin needs to be heated and polymerized within the flask tank with the flask held by the pressing device. Thus, the apparatus is not usable efficiently.
2. The apparatus requires two lids, i.e., the tank lid and the wax lid, and is therefore cumbersome and inefficient to operate.
3. If drops of cleaning water remain after cleaning the pattern cavity created by removing the wax, the presence of water impairs the quality and accuracy of resin filled in. When many flasks are used, the remaining water must be removed from all the flasks reliably during operation without forgetting or failure.
4. A separating agent needs to be applied to the pattern cavity reliably so as to render the filled resin readily removable from the flask after polymerization.
5. The production apparatus must be made compact and less susceptible to work errors to the greatest possible extent.